Drivers of marine heatwaves in the East China Sea and the South Yellow
Sea in three consecutive summers during 2016-2018
Abstract
In three consecutive years from 2016 to 2018, extreme ocean warming
events, or marine heatwaves (MHW), occurred during boreal summers in the
East China Sea (ECS) and South Yellow Sea (SYS), which is unprecedented
in the past four decades based on the satellite record. In this study,
we used a high-resolution hydrodynamic model based on FVCOM (Finite
Volume Community Ocean Model) to simulate the evolution of these warming
events. An upper ocean temperature budget (0-20m) analysis based on the
model results shows that the shortwave radiation and the ocean advection
anomalies jointly contributed to the anomalous warming in the three
successive summers (June-August) in the SYS and the north part of the
ECS. In addition, the reduction of surface wind speeds during the 2016
and 2017 summers further weakened the vertical mixing, thereby enhancing
the anomalous warming in the north part of the ECS adjacent to the SYS.
During the three summers, the increases of shortwave radiation were
closely related to the East Asian Summer Monsoon (EASM) variability,
which reduced the cloud cover in the ECS and SYS, whereas the advection
anomalies were mostly associated with regional wind anomalies. In summer
2018, upper ocean heat was transported into the central trough of the
South Yellow Sea, accumulated in an anticyclonic eddy generated by the
anomalous wind stress curls. Therefore, despite the primary driver of
the MHWs is the EASM variation, regional processes are critical to
driving the spatial pattern of the MHW intensity in the ECS and SYS.